Quizlet is a free online tool that provides flashcards, study games, and tests to help students learn vocabulary and other topics. It was created in 2005 by a high school student and now contains over 400 million user-generated study sets. Users can create their own flashcards with words, images, and definitions and then study using different game modes or take tests. While sets are public, only owners can edit them. Quizlet is easy to use, free, and allows multiple people to study the same sets simultaneously on different devices. It is suitable for all ages and levels due to its simplicity.